Field of the Invention
The present invention relates to a resin composition, coated particles, an injection material and a method for injecting an injection material into a fracture.
Description of the Prior Art
Recently, recovery of oily hydrocarbon or gaseous hydrocarbon (fluid) from a subterranean formation is positively carried out. In particular, a wellbore is formed so as to penetrate a subterranean formation containing hydrocarbon. The hydrocarbon contained in the subterranean formation can be recovered through the wellbore. In this case, the subterranean formation is required to have sufficient conductivity (fluid permeability) to allow the fluid to flow through the wellbore.
In order to ensure the conductivity of the subterranean formation, for example, hydraulic fracturing is carried out. In the hydraulic fracturing operations, a viscous liquid is first injected into the subterranean formation through the wellbore at a sufficient rate and pressure to form fractures (cracks) in the subterranean formation. After that, particles are packed into the formed fractures for the purpose of preventing the fractures from being closed (blocked).
As examples of such particles, Cooke, Jr. (U.S. Pat. No. 3,935,339 A) discloses coated particles obtained by coating core particles such as silica sand or glass beads with an epoxy resin or the like (see, column 3, lines 7 to 21). Further, Graham et al. (U.S. Pat. No. 4,336,842 A) discloses coated particles obtained by coating core particles such as silica sand with a phenol resin or the like (see, column 2, line 55 to column 3, line 52).
Since such core particles of the coated particles are coated with a resin material, even if the core particles are collapsed into pieces due to the earth stresses, it is possible to prevent the pieces thereof from being scattered (spread). This makes it possible to prevent spaces among the coated particles from being closed by the pieces of the core particles, to thereby maintain the conductivity of the subterranean formation. However, from the viewpoints of improvement of an amount of the hydrocarbon recovered from the subterranean formation, it is required to develop coated particles which can keep higher conductivity of the subterranean formation.